What are the difference between tacit and explicit knowledge?

tacit knowlege is knowlege of experience and explicit if knowlege of rationality

Tacit knowledge is the knowing of things without knowing how you know; explicit knowledge is the knowing of things that you can explain. For example, most people can speak grammatically without being able to explain the rules of grammar. This is Tacit knowledge. Explicit knowledge is that answer to 2X2.
In Project Management, Tacit Knowledge is the knowledge your co-worker knows, but isn't codified or written down; while Explicit Knowledge deals with knowledge that is written down and structured. For example, your co-worker knows how to fix Word when it chokes on an important document; but she is the only one. This is the Tacit Knowledge that Project Management tries to root out and codify. Once that knowledge is written down and saved somewhere it becomes explicit.